Tuesday, April 24, 2012

Hiddleston's review of Actuality, Possibility, and Worlds

NDPR has a review of my Actuality, Possibility, and Worlds by Eric Hiddleston.  I think it's quite a helpful review--the concerns about my account are powerful and interesting.

This post is a very rough bunch of responses to Hiddleston, and will not be comprehensible without reading his review.

I am inclined to endorse some version of the "externalist" way out that Hiddleston gives.  I think this will damage at least one of my arguments against Platonism, the one that says that opponents of Platonism are "horribly confused" if Platonism is true. But Hiddleston is right that that's a bad argument.

I think Hiddleston doesn't give enough credit to my dogs argument against Platonism.  There, I am imagining that the Platonist heaven is augmented with the necessity of there being no dogs, but all earthly stuff is unchanged.  I claim in the book that nonetheless dogs would remain possible.  My line of thought behind that was that dogs would remain possible, because they would remain actual, and the actual is possible, no matter what the Platonist heaven says.  I think Hiddleston's Little-P = Big-P position doesn't help here.

(It occurs to me, by the way, that the Platonist could have a theory that escapes my dogs argument as it stands in the book. Here's the theory. The primitive property is mere possibility. Possibility is then defined in terms of mere possibility: a proposition is possible provided that it is either true or merely possible. But I think this version still has a problem. The original Platonic version has the puzzle of why it is that actuality implies possibility. This version doesn't have that problem. Instead it has the problem of why it is that that mere possibility implies non-actuality.)

Hiddleston also worries a lot about Euthyphro-type questions, like:

  • (E1) Why should God be incapable of bringing about really impossible propositions, such as contradictory ones?
  • (E2) Why should God be capable of bringing about really possible propositions?
I think there is a neat counter to the "contradictory ones" part of E1 that favors my view over other views. The following seems true to me:
  1. If, per impossibile, God or any other agent were capable of bringing about a contradictory proposition, that proposition would be possible.
This suggests to me that what agents can bring about is actually more fundamental than what is contradictory. Notice that the plausibility of (1) highlights a difference between my view and divine command theory. In the case of divine command theory, the following seems false:
  1. If, per impossibile, God were to command a horrendous deed, that horrendous deed would be obligatory.
(But see this paper of mine for a more detailed discussion of whether (2) is a good objection to divine command theory.)

I do think Hiddleston's question about what explains why God can do contradictory things is a good and difficult question, but I don't think they're quite species of the Euthyphro problem. I think I can say that there just does not exist any being with the power to bring about contradictory propositions. This is in need of no more grounding than the fact that there are no unicorns--it's just a negative existential. Is it in need of an explanation? My official line on the PSR restricts it to contingent truths. But maybe there still is an explanation of it in terms of some deep facts about the divine nature (maybe its beauty, say). Maybe Hiddleston's best bet here would be to push me in a way that Josh Rasmussen has done: I can't explain why God can't create square circles, just as the Platonist can't explain why everything that's actual is also possible, and so I don't have an advantage over the Platonist here. I don't know exactly what to say here, but I think one difference is with regard to per impossibile counterfactuals.

  1. If dogs existed but the Platonic heaven didn't say that they were possible, dogs would still be possible.
  2. If God were capable of creating a square circle, square circles would be possible.
I think (4) favors my view and (3) disfavors Platonism. But I am not happy to hang too much on per impossibile counterfactuals.

As for (E2), I don't feel the force of that. First of all, the primary view doesn't mention God: it's quantified over all agents. So the modified question is:

  • (E2b) Why should every really possible proposition be such that there is an agent who can bring it about (or, more precisely, bring about a chain of causes leading to it)?
I don't feel much intuitive force to this question. Maybe I've just been thinking along the lines of my view for too long. I am tempted to say that the question is exactly like: "Why should every sample of water contain hydrogen atoms?" That's what Hiddleston labels the externalist way out, so I guess I am with him on that, and I wish I was explicit about that in the book.


Brian said...

I worry that there is an objection to your account which is exactly analogous to your "dog" objection to Platonism. (Though, caveat: I may just be unaware of features of your view which would block this objection) Suppose, per impossibile, that all the agents with the ability to make it true that there are stars (I suspect that this would only include God) suddenly lost that ability, but all worldly facts remain the same. In particular, it remains true that there are stars, even though no agent has the ability to make this true. Intuitively, stars would remain possible, simply because they would remain actual. I don't think you can object to this on the grounds that I'm asking you to suppose something impossible, for the Platonist will also claim that it would be impossible for Platonic heaven to be augmented with the necessity of there being no dogs.

Alexander R Pruss said...

That's OK, because the official account is disjunctive: p is possible iff p is true or something can initiate a chain of causes leading to its being the case that p.